Arizona's splendor is a special blend of naked, thirsty earth, punctuated by many-textured plants of surprising beauty. Since much of the state receives less than 12 inches of annual precipitation, proper irrigation can make all the difference between gardening success and failure. As every Arizonan knows, water is an extremely precious resource in the desert, and managing it wisely can be a real challenge. With attention to detail and careful planning, you can establish a sensible watering regime for a fabulous Arizona landscape.
Water plants in the early morning or in the evening to reduce water loss through evaporation. Avoid watering on very windy days or when there's a chance of natural precipitation.
Build up six inch barriers by packing the soil with your hands to create shallow wells around the drip lines of your plants. This will prevent water from running off and keep mulch over the plant's roots. Expand the wells outward as the plants mature.
Water new plants more often for the first year or two after planting, until they become well established. Give established plants less frequent, deeper soakings to encourage them to develop deep roots. Depending on the species you have, and the weather, you may need to water established plants anywhere from twice a week to once every two weeks.
Soak the plants for as long as it takes to evenly wet the first twelve inches of soil each time you water. You can easily get a feel for how long this will take by pushing a dry, half inch diameter, wooden dowel about a foot deep into the watered soil, avoiding the root ball. Leave the dowel in the ground for a minute or two, and then pull it up and see if it is wet all the way to the end. If not, continue to water until the dowel comes up wet, and then make a note of how long it takes.
Irrigate for three times longer than the usual duration, at least once a year, to leach out accumulated salts from the soil. Do this in late winter or early spring, when desert plants begin their active growing period.